Method for Transferring State Information Pertaining to a Plurality of Sip Conversations

1. A method for transferring state information pertaining to a plurality of SIP conversations from a first SIP server to a second SIP server, said first SIP server and said second SIP server being operatively connected to one or more SIP gateways, the method comprising at a controlling node: monitoring said first SIP server until ongoing transactions are terminated; after termination of said ongoing transactions, obtaining dialog state information pertaining to conversations managed by said first SIP server from said first SIP server; and sending said obtained dialog state information to be stored at said second SIP server.

2. The method according to claim 1 , further comprising suppressing the creation of new sessions at said first SIP server.

3. The method according to claim 2 , further comprising: identifying existing sessions of said first SIP server; initiating interception by said one or more SIP gateways of messages pertaining to new transactions inside identified existing sessions, said interception taking place during said monitoring; and releasing said intercepted messages to said second SIP server after said storing.

4. The method according to claim 3 , wherein said suppressing comprises instructing said one or more SIP gateways to redirect messages pertaining to new sessions to said second SIP server.

5. The method according to claim 3 , wherein said suppressing comprises instructing said one or more SIP gateways to take said second SIP server into use.

6. The method according to claim 5 , wherein said instructing takes place by means of one of a Domain Name System update and a PUBLISH-SUBSCRIBE event.

7. The method according to claim 2 , wherein said suppressing comprises instructing said first SIP server to send a backpressure signal to said one or more SIP gateways prior to said monitoring; wherein, during said monitoring, said first SIP server receives messages in transit from said one or more SIP gateways and returns said received messages to the respective SIP gateways.

8. The method according to claim 7 , wherein said suppressing comprises instructing said one or more SIP gateways to take said second SIP server into use.

9. The method according to claim 8 , wherein said instructing takes place by means of one of a Domain Name System update and a PUBLISH-SUBSCRIBE event.

10. The method according to claim 1 , further comprising sending a first signal and a second signal to said first SIP server, at least one of said first signal and said second signal comprising an identification of said second SIP server; wherein said first SIP server stores messages received from said one or more SIP gateways after receiving said first signal; and wherein, after receiving said second signal, said first SIP server forwards said stored messages to said second SIP server.

11. The method according to claim 10 , further comprising instructing said one or more SIP gateways to take said second SIP server into use.

12. The method according to claim 11 , wherein said instructing takes place by means of one of a Domain Name System update and a PUBLISH-SUBSCRIBE event.

13. A controlling node, comprising: at least one processor configured to: monitor a first SIP server until ongoing transactions are terminated; after termination of said ongoing transactions, obtain dialog state information pertaining to conversations managed by said first SIP server from said first SIP server; and sending said obtained dialog state information to be stored at a second SIP server.

14. A first SIP server, comprising: at least one processor configured to: allow monitoring by a controlling node until ongoing transactions are terminated; and after termination of said ongoing transactions, provide dialog state information pertaining to conversations managed by said first SIP server to the controlling node that is configured to send the obtained dialog state information to a second SIP server.

15. A non-transitory computer readable medium including computer readable instructions, which when executed by a processor, cause the processor to: monitor a first SIP server until ongoing transactions are terminated; after termination of said ongoing transactions, obtain dialog state information pertaining to conversations managed by said first SIP server from said first SIP server; and store said obtained dialog state information at a second SIP server.